With the implementation of a nationwide integrated services digital communications network, a host of new services and features will be available, from conventional voice telephone service to data communication or facsimile. Access to the communications network is made possible via a connecting device to which a communications terminal is connected. Instead of the hitherto used connector socket, a communication connecting unit is now provided (Refer to Unterrichtsblatter der Deutschen Bundespost, Fernmeldewesen, No. 6, 1988, p. 263 et seq).